This has been happening for me quite often recently, and it's strange. I look at my Review Queue, and there's a shining red dot next to the Low Quality Posts. As pictured:
I click on it, and there's nothing - "this queue has been cleared". It's not a situation of caching and refreshing: the red dot stays there for hours, and multiple refreshes. It's even there when I'm on the relevant reviews page, and the page is empty. And interestingly, it's only the red dot that's acting out. The regular grey one works as intended - it's there when there's stuff to review, it's not there when there's nothing.
That's not how it's supposed to work, is it?